Efficient simulation of open quantum systems coupled to a reservoir through multiple channels

Area of Science:

• Quantum mechanics
• Computational chemistry
• Condensed matter physics

Background:

• Simulating open quantum systems with multiple system-bath couplings is computationally demanding.
• Vibrational modes can induce fluctuations in energy gaps and electronic couplings, acting as independent coupling channels.
• These multi-channel couplings are crucial for understanding excited-state radiationless decay processes.

Purpose of the Study:

• To develop an efficient and exact method for simulating the dynamics of open quantum systems with multi-channel system-bath couplings.
• To enable accurate modeling of complex quantum phenomena like singlet fission and exciton transport.

Main Methods:

• Developed an interaction-picture chain mapping strategy for vibrational reservoirs.
• Combined this strategy with density matrix renormalization group (DMRG) and matrix product states (MPS) methods.
• Transformed system-bath couplings into time-dependent, spatially local couplings within the chain-mapped Hamiltonian.

Main Results:

• The interaction-picture chain mapping restricts entanglement to a narrow frequency window, enabling efficient DMRG/MPS simulations.
• Successfully simulated singlet fission dynamics using a generalized spin-boson Hamiltonian with multi-channel couplings.
• Demonstrated the method's ability to handle both diagonal and off-diagonal system-bath couplings.

Conclusions:

• The developed method provides an efficient and exact approach for simulating open quantum systems with multi-channel system-bath couplings.
• This work advances our understanding of nonlocal exciton-phonon couplings and the non-Condon effect in energy and electron transfer processes.
• The matrix product states (MPS) based simulations offer new possibilities for studying complex quantum dynamics.